As hydro Stormbound Men's Outdoor night Jacket Research EqvIwCxw0 age, they produce "onion layers" of heavier and heavier elements in their interiors. However, stars will not fuse elements heavier than iron. Fusing iron doesn't release energy. It uses up energy. Thus a core of iron builds up in the centers of massive supergiants.

Eventually, the iron core reaches something called the Chandrasekhar Mass , which is about 1.4 times the mass of the Sun. When something is this massive, not even electron degeneracy pressure can hold it up.

During the supernova, a tremendous amount of energy is released. Some of that energy is used to fuse elements even heavier than iron! This is where such heavy elements like gold and silver and zinc and uranium come from!